Unlocking the Secrets of Bentonite in White and Rosé Wines

New Insights into Bentonite's Role in Wine Colloidal Stability

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During the recent edition of Enoforum 2024, a session titled "Recent Knowledge on the Use of Bentonite for the Colloidal Stabilization of White and Rosé Wines" was presented, featuring Milena Lambri from the Università Cattolica del Sacro Cuore and María Manara from Dal Cin Gildo S.p.a., Italy, in collaboration with the company DAL CIN. This session addressed topics related to the properties and uses of bentonite in winemaking, a fundamental aid to ensure colloidal stability and the final quality of wines.

Bentonite, widely used in the wine industry, is recognized as the best resource for removing excess proteins in musts and wines. Its application prevents the formation of hazes and the appearance of undesirable deposits in the bottle, issues that can affect the visual and sensory quality of the product. However, the use of bentonite requires detailed knowledge of its characteristics and precise control of the processes to achieve optimal results without altering the aromatic profile of the wine.

Milena Lambri highlighted the importance of bentonite's laminar structure, which is influenced by the presence of exchangeable cations. Properties such as specific surface area and swelling index determine bentonite's ability to remove proteins and other particles. Lambri also delved into the differences between various types of bentonite and their interaction with specific proteins, such as pathogenesis-related proteins (PRs), which include glucanase, chitinase, thaumatin, and invertase. The effectiveness of bentonite in eliminating these proteins depends on factors such as wine pH, ionic strength, sulfite content, and the presence of glycosylated proteins released during fermentation.

Another key point discussed was the potential impact of bentonite on the wine's sensory profile. Non-selective protein removal can lead to a reduction in aromatic compounds that directly affect the wine's organoleptic characteristics. Lambri noted that balancing effective clarification with aroma preservation is a challenge, especially in wines made from aromatic grape varieties, where the presence of aromatic precursors is high and the risk of losing olfactory notes is significant.

Regarding rosé wines, the stabilization of PRs represents a particular challenge. Since these wines often require more intervention to achieve colloidal stability, bentonite application must be carried out with caution to avoid the loss of anthocyanins, compounds responsible for the wine's coloration. Excessive removal of these components can affect the intensity and tone of the wine's color, reducing its visual appeal.

In her presentation, María Manara, head of the R&D department at Dal Cin, discussed how bentonite characteristics can be modulated according to the needs of each wine and the clarification objective. High-purity bentonite, combined with specific activation techniques, allows for different degrees of colloidal stability and protein removal, adjusting to the particular characteristics of the must and wine. Manara explained that the key to effective use of bentonite lies in selecting the appropriate type and applying the treatment at the optimal stage of the winemaking process to maximize haze removal without compromising the wine's sensory profile.

The session concluded with a review of emerging techniques for the use of bentonite in the winemaking of white and rosé wines, emphasizing the need for further studies on its interaction with aromatic and phenolic compounds. The presentations by Lambri and Manara made it clear that the selection and application of bentonite are not only a matter of stabilization but also of preserving the distinctive character of each wine, underscoring the importance of a scientific and personalized approach to the use of this adjuvant in the winery.

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